Whitney Houston died as a result of accidental drowning, but cocaine use and heart disease were contributing factors, a coroner said.

The singer's autopsy revealed traces of marijuana and the prescription drugs Xanax, Flexiril and Benadryl in her body, but not in quantities which would usually prove fatal. The announcement by Craig Harvey, a spokesman for the Los Angeles County Coroner, ended weeks of speculation which began on 11 February when Houston was found submerged in the bath at her suite at the Beverly Hilton hotel.

Mr Harvey, whose office is expected to publish a full autopsy report in a fortnight's time, said that the results indicate that the singer, who was 48 and had spent recent years in and out of rehab programmes, was a "chronic" cocaine user.

She is believed to have suffered a heart attack while alone in the bath, before slipping under the water and drowning. Though the cause remains unclear, cocaine use can act as a trigger in such cases and also causes arteries to harden, exacerbating the effects of an attack.

Houston died on the eve of the Grammy awards, after spending previous days attending a selection of related events.

The news confirms that her death was an accident. Beverly Hills police, who were handling the investigation into the affair, said in a statement that they had uncovered no evidence of criminal wrongdoing.